Magnetic dilution of a honeycomb lattice XY magnet CoTiO3

We report our study of cobalt (II) titanate, CoTiO3, in which magnetic Co ions are replaced by non-magnetic ions. The antiferromagnetic ordering transition of CoTiO3 around 37 K is described with ferromagnetic honeycomb layers coupled antiferromagnetically along the crystallographic c direction. The effect of magnetic dilution on the Néel temperature of this material is investigated through the doping of Zn2+ and Mg2+ in place of Co2+ for various dilution levels up to x + y = 0.46 in Co1-x-yZnxMgyTiO3. Single phase polycrystalline samples have been synthesized and their structural and magnetic properties have been examined. A linear relation between dilution and the Néel temperature is observed over a wide doping range. A linear extrapolation would suggest that the required dilution level to suppress magnetic order is around x + y ∽ 0.74, well beyond the classical percolation threshold. The implication of this observation for microscopic models for describing CoTiO3 is discussed.

Magnetic behavior of Fe-doped of multicomponent bismuth niobate pyrochlore

Two series of iron-containing solid solutions Bi2Mg1− x Fe x Nb2O9+δ and Bi2MgNb2−2 x Fe2 x O9−δ of pyrochlore structure were obtained by the traditional solid phase synthesis method. The electronic state and character of exchange interactions of iron atoms in solid solutions were investigated by methods of magnetic dilution and NEXAFS-spectroscopy. According to X-ray spectroscopy and magnetic susceptibility data, iron(III) atoms are distributed mainly in octahedral positions of niobium(V) and in a dominant amount are in the charge state of Fe(III) in the form of monomers and exchange-bonded clusters mainly with antiferromagnetic type of exchange. Differences in magnetic behavior of iron-containing solid solutions of both series have been revealed. Antiferromagnetic and ferromagnetic exchange can be realized between iron atoms, which, with increasing concentration of paramagnetic atoms and averaging structure distortions, becomes less significant. The parameters of exchange interactions in clusters and distribution of iron paramagnetic atoms depending on the concentration of solid solutions have been calculated.

Study of the nuclear spin and dilution influence over the slow relaxation in a 3d4f heterobimetallic Single-Molecule Magnet

The effect of the isotopic enrichment and magnetic dilution has been investigated in an heterobimetallic complex of formula [Zn2L2ADyCl3]·2H2O] (ADyZn2) (A=162 and 163) presenting slow relaxation of the magnetization. The...

Influence of Nanosize Effect and Non-Magnetic Dilution on Interlayer Exchange Coupling in Fe–Cr/Cr Nanostructures

Magnetic properties of multilayered [Fe–Cr/Cr]×8 nanostructures with the interlayer exchange coupling of the antiferromagnetic type and without the interlayer coupling have been studied. The values of the saturation magnetization and the interlayer exchange coupling constant are shown to strongly depend on the thickness and non-magnetic dilution of the Fe–Cr layers. It is found that those parameters differently affect the interlayer exchange coupling, which is explained by an interplay between the size effect (the thickness of the Fe–Cr layers) and the magnetic polarization of the Fe–Cr/Cr interfaces depending on the Fe concentration.

Preparation and Structural Observation of Co2MnSi Heusler Alloys by Mechanical Alloying

A Co2MnSi Heusler alloy has been prepared by mechanical alloying (MA) method successfully using a mixture of elemental Co50Mn25Si25 powders. A two-phase mixture of amorphous phase and remaining Mn were obtained after 5 hours of MA without any evidence for the formation of Co2MnSi alloys. The saturation magnetization of MA powders decreased with MA time due to the magnetic dilution by alloying with nonmagnetic Mn and Si elements to 48 emu/g after 5 hours of MA. On the other hand, a Co2MnSi single phase was obtained by MA after 3 hours and subsequently heat treated up to 650 °C. X-ray diffraction result showed that the average grain size of Co2MnSi Heusler alloys prepared by MA for 5 hours and heat treatment to be in the range of 85 nm. The saturation magnetization of Co2MnSi Heusler alloys prepared by MA and heat treatment reached a maximum value of 112 emu/g for 5 hours MA sample. It was also observed that the coercivity of 5 hours MA sample annealed at 650 °C was fairly low value of 27 Oe.